A. Technical Field
The present invention relates to an aqueous resin composition and its uses. More specifically, the present invention relates to an aqueous resin composition and its uses, wherein the aqueous resin composition can form such as a coating film excellent in both the blocking resistance and the frost damage resistance.
B. Background Art
Since the past, aqueous coatings prepared from water-soluble resins or water dispersion type resins (e.g. emulsions) have been applied in place of solvent-base coatings in order to avoid environmental problems caused by such as emission of organic solvents into the air. However, when compared with the solvent-base coatings, the aqueous coatings uses water as the medium and therefore have had problems of being inferior in such as driability, durability (e.g. water resistance, weather resistance) and finished appearance of coating films and further involving difficulty in enhancing the hardness of coating films.
In order to solve such problems, attempts are made to enhance the finished appearance and durability (e.g. water resistance) of coating films by such as combining different kinds of emulsions (e.g. refer to patent document 1) or adding specific crosslinking agents (e.g. refer to patent documents 2 and 3).
Generally, when a coating film is formed from a coating, there is a case where the appearance and durability of the formed coating film are spoiled by a phenomenon (which is called blocking behavior) such that the coating film and a layer contacting therewith stick together for the cause that the coating film undergoes pressure during its storage or use. For preventing such a blocking behavior, the coating film needs to be finished into a still harder film. On the other hand, in order to enhance the durability of the coating film during cycles between low and high temperatures, the flexibility is demanded to the coating film. Accordingly, for obtaining the durability of the coating film over a long period of time regardless of rapid temperature variation, it is important to combine the blocking resistance and what is called frost damage resistance.
[Patent Document 1] JP-A-200181/2001 (Kokai)
[Patent Document 2] JP-A-019721/2001 (Kokai)
[Patent Document 3] JP-A-295275/1993 (Kokai)
However, both have trade-off relations with each other, and it is therefore difficult to combine both properties. Thus, it is the present state of arts that the combining of both properties has not come true yet.